martin collins 1 Posted August 3, 2022 Share Posted August 3, 2022 I have to make a canopy for my plan built KI-61, most people use balsa to make a buck for moulding one with a heated pop bottle, has anyone tries foam covered with something to smooth it? Would this work or would the foam just melt under the heat gun? Would be a lot quicker to carve the foam and shape it over balsa. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted August 3, 2022 Share Posted August 3, 2022 It is very tempting to carve up a quick soft former Martin, but that is just the opposite of what you should use that can remain intact under the heat and pressure required to mould a canopy. Â Quote Link to comment Share on other sites More sharing options...
PatMc Posted August 3, 2022 Share Posted August 3, 2022 (edited) Foam would definitely melt at the required temperature. When I've made canopies (+ other odds & ends) from pop bottles I've used off cuts of pine - cheaper (it doesn't come cheaper than free), easily obtainable & more robust to knocks especially if a second one is required later. Mine are rough cut using a band saw then a small plane, a disc sander & finished with wet & dry (used dry).   PS - I've got some pics of my method somewhere on my PC, if I can find them I'll post some on here. Edited August 3, 2022 by PatMc 1 Quote Link to comment Share on other sites More sharing options...
PatMc Posted August 3, 2022 Share Posted August 3, 2022 About 16 years ago I picked up a Protech Unlimited e-glider from a deceased clubmate's estate. It came with two battered blown plastic fuselages but no canopies. The main section in the photo is the actual canopy shape the base & ply end pieces were added to allow an oversize finished article that would be trimmed to fit. It's fixed to a batten from underneath by a couple of long screws. The whole lot is from scrap wood left over from DIY projects.     Prep - add a pair of oven gloves & a pair of pliers.      The mounting batten also proved the bulk underneath to get the size within the shrinkage limit. 2 Quote Link to comment Share on other sites More sharing options...
PatMc Posted August 3, 2022 Share Posted August 3, 2022 I think the canopy in the previous post was a first try that was scrapped but I made a number of useable canopies from green, brown & plain bottles for myself & someone on a forum.   One of the fuselages was used for a slope soarer.    The other as designed but with lipo & brushless motor.   This fibre glass moulding was made by leaving a shrunk down bottle on the former, trimming the bottle neck away, laying up FG & resin on top then while the resin was still wet shrinking down another bottle over it.   When painted the finished is "stand off" acceptable. 5 Quote Link to comment Share on other sites More sharing options...
Andy J Posted August 4, 2022 Share Posted August 4, 2022 I tried using a blue foam inner with a plaster of paris skin and found that the outer shell cracked when used as a plug in my vacume mold set up. A solid plaster plug did work OK for another larger canopy but it did have surface damage after its first use. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted August 4, 2022 Share Posted August 4, 2022 I've had success with wooden plugs, like those featured in Pat's pictures, with plaster of paris -multiple pulls possible with care - and latterly, most surprisingly, with 3D printed PLA plugs in my vac-former. I don't think either pink or blue foam would stand the heat required to make PETG or similar workable enough to make a good canopy. Quote Link to comment Share on other sites More sharing options...
Guest Posted August 4, 2022 Share Posted August 4, 2022 Nice one Pat,now I know where to come when I need a canopy. Top Job. Jim 😎 1 Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted August 6, 2022 Author Share Posted August 6, 2022 (edited) I thought i would persevere with the foam plug idea as it so much quicker to shape and sand, i used some of that insulation board that has the silver foil on both sides. The heat gun didn't seem to melt it so i made the plug, gave it several applications of Easy-kote then primed and top coated it yesterday. Today i shoved it in a pop bottle and formed it with my heat gun. Some of the paint came off on the canopy but i removed that with thinners and trimmed it down. Here are the results, very pleased with it, canopy glue has just gone on in the picture, i will paint the frame tomorrow. So result is you can use foam but obviously only certain types. Edited August 6, 2022 by martin collins 1 4 Quote Link to comment Share on other sites More sharing options...
MikeQ Posted August 7, 2022 Share Posted August 7, 2022 Hi foam works just fine depending how much heat you are using.  Ive recently gone from ‘zero to hero’ in my own estimation 😀 using vac forming.  Like a lot of things, its a lot easier than it looks.  Ive used foam, liteply and 1/16 ply, glassed, to ‘build’ the plug.  Glassed with 3/4 oz and wet sanded smooth.  Takes a couple of hours end to end but us very rewarding.   3 Quote Link to comment Share on other sites More sharing options...
MikeQ Posted August 7, 2022 Share Posted August 7, 2022 (edited) This stuff worked great and its A3 sized.  A4 is also available ... https://www.amazon.co.uk/gp/product/B07NGM3CCR/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1 This is useful for a the plastic pipe that fits Henry styke vacuums ... https://www.ebay.co.uk/itm/182227316539?var=484422434514  the oher essential is a wife who is happy for you to use her oven.  mike  PS the vac boxes are actually 3/4 full of foam to reduce the volume of air that needs sucking.  Big one has a socket  each side as she has a house Henry and I have a workshop one.  In the end i only needed one vacuum cleaner, the other socket being ‘blanked off’.    Edited August 7, 2022 by MikeQ 2 1 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted August 7, 2022 Share Posted August 7, 2022 Couple of very good tips there - thanks so much for that. Taking the staples out of the edge of the PETG sheets is a bit of a pain on my frame, and reducing the internal volume of the A3 sized vac box to increase the suck is something I'll definitely try. 😎 Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted July 6, 2023 Share Posted July 6, 2023 Yup - thanks for the tips 🙂 I tried vacuum forming a while back and failed pretty miserably, so above hints and tips have rekindled my enthusiasm.  I particularly like the taping off of redundant holes to increase the suction round the mould 🙂 Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted July 6, 2023 Share Posted July 6, 2023 Help! I have just managed to get fusion 360 to generate a rough spitfire mk24 canopy shape (took ages as first attempt at lofting 🙄). Had not really got as far as to thinking about how to use it  to form the canopy!! as I was using it to come up the (for me, very steep) learning curve on the 3D modeller. Had vague thoughts of using Easycomposites XCR epoxy coating resin to produce a mould and then tool but this seems overly complex. Am tempted to try sanding and then covering in polymeric vinyl or easycoat x 3 as suggested above. I'm a bit worried about covering it without wrinkles as it is quite curvy.:    Printed with in PLA with .4mm nozzle and .3mm layers.  Likely to try plastic bottle and heat gun to start as I think I deconstructed the vacuum box 😞  Any suggestions as to covering material, approach or other useful threads very much appreciated! 1 Quote Link to comment Share on other sites More sharing options...
MikeQ Posted July 7, 2023 Share Posted July 7, 2023 (edited) Hi, 25g glass cloth, in or ot two layer and finishing resin (not regular epoxy for gluing stuff together) can be sanded , body filled, primed super smooth.  Bit pricey though unless you already have some on hand though.  Regular epoxy might well be just as good but the one time i tried using it, it didnt come out as hard and wasn’t as easy to spread unless thinned (which is why it probably didnt end up as hard in the first place)  That would be my recommendation.  cheers  Mike Edited July 7, 2023 by MikeQ 1 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted July 7, 2023 Share Posted July 7, 2023 You could always do it the other way around, 3d print the canopy as a female mould, and then mould it in plaster of paris, most of my cockpit mould are made this way . 2 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted July 7, 2023 Share Posted July 7, 2023 (edited) Is it just the fine lines on the 3D print that you are looking to eliminate or is it concerns that the 3D printed plug will melt on application of heat?  If it's the former, that could be alleviated by a little wet sanding with very fine wet and dry paper. An alternative is the polymer coating for 3D prints, which is a bit messy, mucks up the dimensions a bit, but does produce a very smooth flow coat finish - probably better for figures than engineering objects though and I'm not sure how that would stand the rigours of heating.  If it's the latter I was pleasantly surprised to find that the PLA plugs that I had printed for my Dornier DO17 canopies were able to be used for at least four vac-forming attempts to produce an acceptable canopy, without any noticeable degradation. I'd be happy with that for a plaster of Paris plug- can't vouch for the integrity in producing a large number of canopies but might be worth having a try to simplify the process. My original intention had been to use the PLA male plug to create a glassfibre female mould and then a Plaster of Paris replica of the original 3D printed male plug. However I decided to just experiment and give it a try on the PLA master plug and it worked.   Edited July 7, 2023 by leccyflyer 1 Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted July 7, 2023 Share Posted July 7, 2023 Many thanks for all the suggestions guys. MUCH appreciated 🙂 Yes, I am rather worried about the PLA melting, but am now very tempted to sand with say 500 git (?) and then have a go with a bottle! Afterall, I only need one canopy 🙂 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted July 7, 2023 Share Posted July 7, 2023 That's the ticket - even if it melted, you could always print another one and start again. 1 Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted July 9, 2023 Share Posted July 9, 2023 So I was lazy and tried the prototype directly in a bottle with heat gun 🙂   Trouble is, it's actually quite a small canopy and needs quite a bit of heat to shrink onto the plug which has distorted the plug but not as much as you would think given the level of heat used. Interestingly you could see the pattern of the 3D print support structure beginning to emerge 🙂  The bit that killed it was a wrinkle I could bot get out (green).   So before I attempt to smuggle plastic into the oven I'm going to try dividing the plug up into bits to reduce the shrinking requirements:  So am now printing:  Green bit is front canopy, purple is support so I don't melt the corners of the plug as much as I did last time 😊    Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 9, 2023 Share Posted July 9, 2023 (edited) @Mike ChantlerDid you use a void filler as in my post dated 3 Aug 22 above ? Edited July 9, 2023 by PatMc Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted July 9, 2023 Share Posted July 9, 2023 Yes, and thanks for the tips. I maybe should of made the void filler a better fit:   Problem is that it fall off quite quickly at both the front and back.    But will be more careful with the void filler next time.  Mike Quote Link to comment Share on other sites More sharing options...
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